Road surface



Oct. 5, 1943. c, BINGHAM 2,330,808

ROAD SURFAC E Filed March 7, 1941 2 Sheets-Sheet 1' WITNESS m INVENTORATTORN EYS Oct. 5, 1943.

E. C. BINGHAM ROAD SURFACE Filed March 7, 1941 2 Sheets-Sheet 2 N i if i/45 TlIlTlU- V r S WITNESS E INZYENTOR/I/ g UGEA/E .jm a 14M ATTORNEYSUNITED STATES PATENT OFFICE ROAD SURFACE- Eugene C. Bingham, Easton, Pa.

Application March 7, 1941, Serial No. 382,132

12 Claims. (Cl. 94-1) My invention relates to improvements in roadsurfaces and its general object is to provide an improved road surfaceof simple, reliable, and inexpensive construction wherewith it ispossible to obtain maximum illumination thereof by the lamps of thevehicles which it carries.

The problem of properly illuminating roads to provide for safe nightdriving has been of pressing importance in recent years due to theincreasing number of accidents which occur after dark It has beenestimated that sixty percent of the deaths on highways occur after darkalthough there is then only twenty-five percent as much traflic. In anattempt to alleviate this condition, it has been given a great deal ofpublicity of an educational nature and many suggested systems of highwaylighting have been experimentcd with. Some of these lighting systemshave proved fairly satisfactory and if their use results in asulficiently marked drop in the casualties on those highways on whichthey have been installed, they will no doubt be used on an increasingnumber of roads. But this expansion has an obvious limitation due to theheavy expense for installation and maintenance of such lighting systemsand, in all probability, will not spread beyond the important orprincipal highways into the secondary roads which form the greater part,by far, of the highway system of this country. Efforts in otherdirections to provide a less expensive solution to the problem have ledto the devising of various kinds of markers to be anchored in the roadand to the incorporation in suitable road binders of light reflectingmaterial. Markers are' so costly that their use, in the main, has beenlimited to designating functions and to defining road limits.Furthermore, known types of markers have a very low efliciency as lightreflectors and they are prone to work loose from the roadway after beingsubjected to the strains inflicted by trafiic. The use of lightreflecting material in the road surfaces is ineificient andunpredictable because the positions of the particles of such materialcannot be controlled.

Realizing the shortcomings of the methods heretofore suggested, I made acareful study of the problem to determine if a more effective andreliable solution could be devised. I found that roads having a smoothasphalt surface were least illuminated by the lights of a vehicle. This,I believe, is not due to the dark color of this type of road but to thefact that when a perfectly smooth horizontal surface is illuminated bylights striking it at a very low angle, as in the case of the light fromthe headlamps of an automobile,

it offers the worst possible condition for illumination, particularlyso, when such a surface is wet as it is then converted into an opticalsurface, meaning that it gives specular reflection like any mirror. Thisbelief is borne out by the fact that when I placed a well-planed boardcoated with several layers of flat-white paint upon a road surface wherethe lights of a vehicle could strike it, the white surface did notappear bright as I had expected but appeared to be even darker than theroadway itself due, no doubt, to the fact that the smooth coating ofpaint presented a better reflecting surface than did the surface of theroadway. On the other hand, a pavement covered with gravel was much moreluminous than one without and it did hot seem to make any differencewhether the gravel was made of light material or dark, for the gravelcouldbe covered over with an asphalt coating, and yet become quite asluminous as the uncoated light colored gravel. From these observations Iconcluded that whether the road was made of light or dark material wasnot of prime importance, that smooth surfaced roads offered the worstpossible condition for illumination by the lights of a vehicle and thatthis condition was aggravated by paint, horizontally-positioned metal orlight-colored nonmetallic materials which ofier'better reflectingsurfaces to the beams of light, and that the only part of the lightgiven out by the lamps of the vehicle that was of any use to me indriving was the part of the light that went out to the pavement and thenreturned to my eyes. Further research showed that while gravel andtransverse ridges resulting from irregularities in the road surfaceincreased the visibility of the road to some extent, the effect wassmall and insuficient to be of any material assistance to the driver.This, I found, was due to two factors. In the first place, only a verysmall portion of the light from the lamps of a vehicle falls on the roadand such light as does fall on the road decreases so rapidly inintensity in its travel from the vehicle lamps that the light at adistance of one foot from the lamps of the vehicle is reduced to anintensity of less than one one-hundred thousandth part at a distance ofthree hundred and twenty feet from such lamps. As the surfaces of graveland irregularities in the road do not concentrate the light striking itat such distance but, on the contrary, usually diffuse it in alldirections, the light will spread out in all directions on returning andonly a very minute part of the light will return to the eyes of theoperator of the vehicle. In the second place, the lamps of a vehicle arenormally about three feet above the pavement, so that, that portion ofthe light which strikes the pavement at a distance of three hundred feetfrom the car, strikes it at the extremely low angle of about 0.5 degree.As gravel or irregularities in the road surface rarely have surfaceswhich approach within one-half of a degree of the vertical. it is clearthat the ordinary gravel particles or the ridges formed byirregularities in the road surface do not increase greatly thevisibility of the road but, on the contrary, tend to reflect the lightin directions away from the operator. Furthermore, as at this angle, thelight beams are Just grazing the road surfaces, the pieces of gravel andirregularities near the vehicle will in all likelihood interfere withthe light reaching the gravel or irregularities farther away. Thus,while the gravel or irregularities immediately in front of the vehiclemay be sufliciently illuminated, the visibility will decrease so rapidlywith the distance that at normal driving speed the eyes of the driverare taked to see the highway at the more remote distances, let up say,two hundred and flfty to three hundred feet. I found, however, that bydeliberately roughening or constructing the road surface in a specialmanner I was enabled to increase the illumination thereof to such anextent that at those parts spaced from the vehicle where lightvisibility is desired by the operator of the vehicle, such parts wereclearly visible to the operator and the major factors which caused pastdifliculties were eliminated. The principle involved is based upon aconception that reflecting surfaces provided in the roadway should be sooriented in an exact position with respect to each other and to thevehicle as to return to the operators eyes a maximum of the amount oflight which falls on the road at a distance, of say, three hundred feetfrom the lamps of the car. I am aware that it has already been proposedto provide blocks having surfaces which are presented in opposedrelation to the direction of the travel of the vehicle so as to reflectthe light rays coming from the lamps of the vehicle, but so far as I amaware such blocks were so constructed that their illuminating effectswere practically negligible at substantial distances from the vehiclefor one or more of the reasons previously pointed out.

For a clearer understanding of the invention I have made, based on theprinciples and discoveries made during the course of my study of thisproblem, reference is made to the following description to be read inconnection with the accompanying drawings, in which Fig. 1 is a planview of a double highway constructed in accordance with the invention;Fig. 2 is an enlarged fragmentary sectional view of the highway shown inFig. 1 taken along the line 2-2 of Fig. 1; Fig. 3 is a similar viewtaken along the line 3-3 of Fig. 1; Fig. 4 is a vertical sectional viewof a portion of a highway built with blocks in accordance with theinvention; Fig. 5 is a side elevational view of a modified form of blockthat may be used in the construction of the highway; Fig. 6 is a viewsimilar to Fig. 5 showing another type of block that may be used; Fig. Wis a plan view of a curved portion of a single-lane highway made inaccordance with the invention; Figs. 8 and 9 are vertical sectionalviews of modified forms of paving bloclm, and Fig. 10 is a plan view ofthe crossing of two highways, to illustrate the manner in which theinvention may be utilized at such cross- In Fig. 1 of the drawings, thedouble highway is shown with two vehicles l0 and ii traveling inopposite directions and being provided with the usual headlamps. For thesake of simplicity, no account has been taken of the distance separatingthe two headlamps of each vehicle, the headlamps of the two vehicles [0and H being illustrated as single unitswhich are designated by thereference characters l2 and I3, respectively. As is usual, the lamp i2of the vehicle In concentrates the light emanating therefrom so that themajor portion of such light striking the highway falls upon the lane Mof the highway, while the light from the headlamp B on the vehicle I ltraveling in the opposite direction is concentrated to illuminate thehighway lane l5. Each of the road lanes l4 and i5 is composed of aseries of transverse rows of reflecting surfaces, the rows 'of thehighway lane ll being indicated by the reference numeral l6 and the rowsof the highway lane 15 being indicated by the numeral I1. The reflectingsurfaces in each case are arranged to face the path of travel of thevehicles so that the reflecting surfaces of lane l4 will face in adirection opposite to that of the surfaces of lane l5, as will bereadily evident from a comparison of Figs. 2 and 3 of the drawings. Thereflecting surfaces may be formed by specially arranged or speciallyconstructed blocks, by embossing the road surface, by inserting metalstrips, etc., all of which will become hereinafter more clear. In Fig. 4of the drawings, there is shown by way of example, a method of formingthe rows of reflecting surfaces by means of bricks or blocks. Referringto Fig. 4, the blocks IU of each row may be rectangularly-shaped andlaid in slightly tilted position upon the roadbed l9 so that each brickpresents an elongated rectangularly-shaped surface 20 to the view of theoperator of the vehicle traveling on such highway. As the bricks orblocks 18 are tilted so that the surfaces 20 thereof in each highwaysection or lane is opposed to the direction of the travel oi vehicles onsuch lane, it will be evident that the blocks l8 on one lane, say lanel4, will be tilted in a direction opposite to that of the blocks on thelane i5, compare for example, Figs. 2 and. 3 of the drawings. Thus eachlane of the highway is constructed of a series of rows of bricks tiltedto present a plurality of reflecting surfaces 20 in opposed relation tothe direction of travel of traflic on such highway lane so that beams oflight from the headlights of the vehicles will strike against suchsurfaces. The angle of tilt of each brick is determined by the averageheight of the lamps of vehicles from the road surface, and by thedistance from the vehicle at which it is desired to have the roadilluminated. The heightof the reflecting surfaces 20, which are arrangedso as to be perpendicular or normal to those rays of light emanatingfrom the headlamps of a vehicle and striking the roadway at the distancefrom the vehicle at which visibility i desired. is determined by thesize of the blocks that it is convenient to use. For example, let it beassumed that the highway is to be constructed so that the light from avehicle is to illuminate the road for a distance of from two hundred andfifty to three hundred feet from the vehicle. As the headlamps of thevehicle are usually positioned at about three feet above the surface ofthe highway, at three hundred feet from the vehicle rays of light fromthe headlamps would be striking the pavement at an angle with thehorizontal which corresponds tothe tangent of three over three hundredor approximately zero degrees, thirty-four minutes. This angle will beequal to the angle between the face of the surfaces 20 and the vertical,when the former are positioned so that they are normal to those beams oflight reaching from the headlamp at a distance of three hundred feet andtherefore in position to reflect the light back to the vehicle. In otherwords, in order that a maximum of the 11gb from the headlamps of thevehicle be reflected back to the eyes of the operator from a distance ofthree hundred feet, the angle which each surface 26 makes with thevertical should be equal to the angle which the top surface of the brickor block It makes with the horizontal and should be approximatelyone-half of a degree. For the sake of simplicity, it is here assumedthat the line from the lamp of a vehicle to the pavement at threehundred feet is coincident with the line taken by the light in returningfrom the pavement to the operator of the vehicle. Thus none of the lightwill strike the top surfaces of the blocks at this distance but will allshine directly on the opposed reflecting surfaces 26 of the blocks. Inorder that there may be no interference with the light rays strikingeach surface 20 (see Fig. 4) at the considered distance, the height ofthe latter is in the same ratio to the length between the bottom of onereflecting surface and the next, as the height of the vehicle lamp(three feet) is to the distance of such surface 20 from the car (threehundred feet). Thus if the length of the blocks is one inch, the heightof the reflecting surface 20 which can be illuminated from the headlampof the car at three hundred feet will be 0.01 inch, while if the lengthof the block is made two feet, the corresponding height of the surface20 will be 0.24 inch. Thus even if the surfaces 20 are two feet apart,the height of such surfaces which are usable as reflectors is onlyone-quarter of an inch. It will be understood that with effective orusable reflecting surfaces one-quarter inch in height, for illuminatingdistances of three hundred feet, the distance of two feet is to be takenas a minimum, for, of course, the distances between such surfaces can begreater than two feet depending upon the degree of illumination of theroadway desired. At distances greater than two feet the height of thesurfaces 20 can, of course, also be correspondingly greater and sincethe wave length of light is of the order of a ten-thousandth of an inch,it is not at all necessary for the reflectors to be large andconspicuous and may be reduced to less than one-quarter of an inch. Ineither case, whether the distance between reflectors is less than orgreater than two feet, the light reflected should be constant, it beingunderstood that when the distances between reflectors are less than twofeet, the effective or usable reflecting surfaces will becorrespondingly reduced. The factor determining the maximum distancemight be the riding quality of the highway and the factor determiningthe minimum distance would in theory be the wave-length of light, of theorder of a tenthousandth of an inch, but in practice it might welldepend upon the feasibility of constructing a large number of reflectorshaving the required reflecting properties over a long period of time.

It will be evident from the foregoing that if the blocks la in the roadare laid in the manner described, none of the light from the lamp f thevehicle will strike the long slope or top surfaces of the blocks butwill strike the reflecting surfaces 26 perpendicularly to the directionof its travel and will be reflected therefrom back to the eyes of theoperator. Any light coming from the opposite direction, as from thelamps of a vehicle traveling in the opposite direction will, however,strike the sloping top surfaces of the bricks and will be reflected awayfrom the lamp of the vehicle from which it emanates. It will thus appearthat the driver of the vehicle will see clearly illuminated only thathalf of the road on which he is driving, while the other lane of theroad for traillc in the opposite direction will appear to besubstantially dark and unilluminated.

The optical quality of the reflecting surfaces 20 of the blocks is of asgr mp t nc as is the proper placing of each block in order to obtainwhat may be properly described as the focusing of the light. Thereflecting surface 20. of each block should not only be true in shapeand smooth but it should also have a highly polished surface for thebest effect. The reason for this is that the wave length of light is sosmall that even a large number of minute irregularities in thereflecting surface will reflect the light in all directions with theresult that the reflected light will be highly diffused and will notreturn to the operator. In this connection, glazed bricks provideexterior surfaces which are highly effective as reflectors. Equallyeffective results are attained by providing on the reflecting surfaces20 strips of chromium-plated metal or coats of material having highreflective qualities, such as, aluminum paint or paint containing metalflakes or mica provided that it dries to a glossy surface. Even a darkcolored asphaltum or plastic material may be utilized providing it isglossy and does not attract dirt. Preferably also, in view of the factthat the light from the lamps of a vehicle spreads out in all directionsalong an arcuate front, the rows of blocks should be arcuately arrangedin order to reflect back the maximum amount of light to the driver. Thismethod of arranging the bricks is illustrated in Fig. 1 of the drawingswhere the rows 06 and l? are illustrated as having a slight curvature,the dotted line extensions of the rows at the ends of such figureindicating more clearly the different horizontal curvatures of the rowsin the two lanes Hi and l 5 of the highway. The curvature of the rows,under the conditions described. would for a twenty foot pavementcorrespond approximately to a deviation from a straight line of nearlyfive inches. While i have by the foregoing description indicated thatthe reflecting surfaces should be flat, for best results the surfacesshould also be arcuately shaped so that the curved rows of reflectingsurfaces present approximately spherical segments.

Instead of making the blocks of a rectangular form, as is illustrated inFig. 4 of the drawings, the blocks may be made with a longitudinalsection of such trapezoidal form as to provide a small reflectingsurface arranged at the correct angle for maximum refl ction under theconditions desired. Such abrick or block is designated 2! in Fig. 5 ofthe drawings. the refl cting face 22 thereof being formed at one end ofthe brick and being smooth and glazed or painted to increase itsreflecting qualities. Blocks of this type may be readily laid in rows ona flat surface with the reflecting surfaces properly positioned toreflect amaximum of the light back to the eyes of the operator and witha minimum of expense and trouble. The blocks can be made also with theend faces thereof parallelly arranged with respect to the reflectingsurface, as is illustrated by the that when such blocks are laid uponthe roadway there is an interlocking condition between the blocks.

From the foregoing, it will be understood that the height of thesurfaces is determined by a number of considerations among which may beadded convenience and expense of production,

ease of riding and effects of wear. Thus the user has a wide latitude ofchoice, but after the center of area of greatest illumination and suchother considerations are determined upon, the angle of the reflectingsurface for each block is fixed. If

' the upper surface of the blocks are true, the reflecting surfaces donot need to be as much as one-eighth of an inch in height but underactual operating conditions no noise or discomfort has been noticed inriding over samples with reflectors a quarterv of an inch in height. Ofcourse, instead of utilizing blocks, the same effects can; be obtainedin macadam and concrete roads by either working the road surfacingmaterial when it is soft in some appropriate fashion, as by rollers orother tools or machines, to emboss upon the road surface a fundamentalsurface configuration provided with reflecting surfaces which can bemade better reflecting by means of paint, or setting or driving into thejoints or body of the pavement wher feasible, reflecting strips of thedesired configuration. As visibility of the highway depends uponcontrast, there is no need for a middle line at night because thepavement in the reverse direction will appear black. This is due to thefact that the light from an oncoming vehicle strikes the slopingsurfaces of the pavement between the reflecting surfaces and will bereflected away from the eyes -of the observer. Should it be desired,however, to mark lines between two or more lanes in the same direction,this could be managed by simply leaving out the reflecting feature froma six inch strip which would then appear dark by contrast, or, thehorizontal curvature of the end portions of the rows of reflectors couldbe increased so as to bring the gleam in the strip closer to the car.This feature is best illustrated in Fig. 7 of the drawings, in which thetransversely extending lines 2E indicate the arrangement of the rows ofreflectors which are so arranged as to provide the maximum amount ofreflection for the vehicle traveling in the direction of the arrow andthe shorter lines designated by the numerals 25, 25 indicate reflectingsurfaces so positioned at the sides of the road as to bring the gleam ofsuch reflectors closer to the car, it being understood that the closelyplaced lines at the upper end of Fig. '7 represent more truly therelation of the surfaces to one another while the more widely spacedlines indicat generally the directions of the rows on the severalportions of the curve. The sides of the road, at a given angle, willthus appear brighter than the body thereof and by such contrast willclearly indicate the limits of the road. If the sides of the roadway areraised, as in the case of curbing, the upper surfaces of the raisedsides should be provided with reflecting surfaces and the inside wallsof the raised sides should preferably be constructed to present inclinedouter surfaces arranged to deflect the beams of light flecting surfacesat such curved portions of the road. The horizontal radius of curvatureof the rows may-also be considerably decreased at the curves of throadway and the rows of reflectors diverge from one another to an extentdepending upon the curve to make the pavement of the curve visible tothe operator for as great a distance as possible. Furthermore, where itis desirable that road signs be placed for the convenience ofthetraveler, as at intersections, it has been found that by removing thereflecting surfaces at th portion of the road where the letters ordesignating signs are needed, such characters will appear black and insharp contrast against the light background produced by the lights of avehicle, thereby providing a clearly distinguishable sign for theconvenience of the operator of the vehicle. As such signs can be placedin the middle of the roadway where they will be the most conspicuous,the attention of the operator can be maintained on the highway itself.

In view of the fact that at distances of three hundred feet from thevehicle the beams of light do not strike the road surface at anappreciable angle but just graze this surface, any imperfections in thesurface or particles resting thereon may tend to interfere with thebeams properly striking or reaching the reflecting surfaces. In order toobviate any possibility of this occurrence, the top surfaces of thebricks may be configured in the manner illustrated in Fig. 8 of thedrawings. In this figure, the dotted line designated by the numeral 26indicates the path of the beams of light from the headlamps of a vehicleat a distance of three hundred feet from the vehicle. The upper surfaceof the block or road, intermediate the two reflector surfaces 21, 28, isformed to provide a relatively steep surface portion 29 immediately inback of the reflector surface 2'! and a substantially horizontallydisposed surface portion 30 extending up to the reflector surface 28.Thus as these surface portions are substantially below the path oftravel of the light beams 26 from the vehicle, any particles or bodiessuch as the particle designated 3| in Fig. 6 of the drawings, Will notinterfere with the light striking the reflecting surface 28. Theincrease in the angle of the non-reflecting face or top surface of thebrick has two further advantages, in that, in the manufacture of thebrick blocks, it is a matter of convenience not to have the maximumangle of precision to the bottom of the trough. On the other hand, agradual increase in the angle of the reflecting surface with thevertical has the effect of-increasing the visibility of the highway atdistances nearer than three hundred feet, which is highly advantageous.Instead of configuring the blocks or road surface in the mannerillustrated in Fig. 6,- they may be given other forms capable ofaccomplishing the desired results, as for example, a form such as isindicated by the reference numeral 32 in Fig. 9 of the drawings. Also,instead of providing only a single reflecting surface on the blockshereinabove described, each block may be provided with a plurality ofreflecting surfaces arranged one behind the other, it being understoodthat the features of construction of the above described blacks will beduplicated in such compound blocks by the number of reflecting surfacesprovided thereon. At intersections of a highway, the reflecting surfacescan be laid so as to indicate the approach of vehicles coming from otherdirections. This is illustrated in Fig. 10 of the drawings, which showsa typical intersection of two highways 45 and 46, each of which, may bebuilt in two lanes in the manner previously described. In the area, ofintersection, there are provided four L-shaped portions 33, 34, 35 and36 in which the rows of reflecting surfaces are arranged so that theyreflect the light beams from vehicles traveling in the variousdirections on such roads in the manner indicated by the right angledarrows 31, 38, 39 and 40. Since, in Fig. 10, the roads 65 and d6 crossat right angles the reflecting surfaces are set at an angle offorty-five degrees to the traffic lanes, as is indicated by the crosshatchings in the L-shaped portions 33, 34, 35 and 36. Thus beamsof lightfrom a vehicle traveling in the direction of the arrow 4| will bereflected by the reflecting surfaces in the L- shaped portion 3% in thedirection of arrow 40 to warn the operator traveling in the direction ofarrow M of such vehicles approach to the intersection. At the same time,the beams of such vehicle will be reflected by the reflecting surfacesin the L-shaped portion 33 in the direction of arrow 38 to warn theoperator traveling inthe direction of the arrow 42. Similarly, operatorstraveling in the directions of arrows 4i and 43 will be warned of theapproach of an operator traveling in the direction of arrow 4!,operators traveling in the directions of arrows t2 and M will be warnedof the approach of an operator traveling in the direction of arrow 53,and operators traveling in the directions of arrows ti and 43 will bewarned of the approach of an operator traveling in the direction ofarrow 45:. The reflected light thus serves to warn vehicles approachingthe intersection well in advance, but in the absence of cars approachingthe intersection all of these panels will remain dark because they areplaced at the wrong angle to return light to the driver. The L-shapedform of the portions 33, 3t, 35 and 36 indicate more clearly to theoperator the direction of approach of a vehicle on the cross highwaywithout diverting his attention from the highway and is especiallyadvantageous if the road is made blind by buildings, shrubbery, signs,etc. Of course, if the two highways meet at an angle other than ninetydegrees, the reflecting surfaces will be arranged so as to reflect thelight into the other sections of the road in the manner indicated toforewarn the driver of the approach of a car from another section of theroadway.

I claim:

1. A road surface of such smoothness as to offer no materialinterference to the passage of a vehicle thereover and capable of beingrelatively brightly illuminated at substantial distances by a lightsource carried by the vehicle, said road surface comprising a series ofreflecting surfaces arranged to face the path of travel of vehiclesthereon, said reflecting surfaces being substantially normal to lightbeams from such vehicles and disposed from the vertical at an anglewhose tangent is the ratio of a predetermined height of a source oflight positioned. above the road surface at a predetermined substantialdistance from and in front of such reflecting surface to the horizontaldistance between such light source and the reflecting surface, wherebysuch reflecting surfaces provided in a substantially level section ofroadway so as to be illuminated as aforesaid at a distance of aboutthree hundred feet from a vehicle on such roadway section and havinglamps positioned at about three feet above the roadway will be disposedat an angle of approximately one-half a degree from the vertical.

2. A road surface of such smoothness as to offer no materialinterference to the passage of a vehicle thereover and capable of beingrelatively brightly illuminated at substantial distances by a lightsource carried by the vehicle, said road surface comprising a series ofreflecting surfaces arranged to face the path of travel of vehiclesthereon, said reflecting surfaces being substantially normal to lightbeams from such vehicles and departing from the vertical at an anglewhose tangent is the ratio of a predetermined height of a source oflight positioned above the road surface at a predetermined substantialdistance from and in front of such reflecting surface to the horizontaldistance between such light source and the reflecting surface, wherebysuch reflecting surfaces provided in a substantially level section ofroadway so as to be illuminated as aforesaid at a distance of aboutthree hundred feet from a vehicle on such roadway section and havinglamps positioned at about three feet above the roadway, will be disposedat an angle of approximately one-half a degree from the vertical, andsaid reflectors being spaced from each other longitudinally by adistance at least equal to the quotient obtained by dividing the heightof that portion of the reflecting surfaces to be illuminated by thegiven ratio.

3. A. road surface such as defined in claim 1, in

which said reflecting surfaces are arranged in rows extendingtransversely of the roadway and in which the reflecting surfaces of eachrow are for the major portion at least disposed at an angle other thanninety degrees to the longitudinal central line of the roadway.

- 4. A road surface of such smoothness as to offer no materialinterference to the passage of a vehicle thereover and capable of beingrelatively brightly illuminated at substantial distances by a lightsource carried by the vehicle, the said road surface comprising a seriesof refleeting surfaces, each of which departs from the vertical at 'anangle whose tangent is substantially the ratio of a predetermined heightof a source of light positioned above the road surface at apredetermined substantial. distance from and in front of such reflectingsurface to the horizontal distance between such light source and thereflecting surface, whereby such reflecting surfaces provided in asubstantially level section of roadway so as to be illuminated asaforesaid at a distance of about three hundred feet from a vehicle onsuch roadway section and having lamps positioned at about three feetabove the roadway, will be disposed at an angle of approximately onehalfa degree from the vertical, said reflecting surfaces being substantiallynormal to light beams from such predetermined source and the roadsurface between reflecting surfaces having a height less than that ofsaid reflecting surfaces and a length at least as great as the quotientobtained by dividing the height of that portion of the reflectingsurface to be illuminated by the given ratio.

5. A road surface such as defined in claim 4, in which the road surfacebetween longitudinally arranged reflecting surfaces extends from thebottom of one of such surfaces to the top of an adjacent reflectingsurface,

6. A road surface such as defined in claim 1, in which said reflectingsurfaces have a height greater than the portion thereof to beilluminated at the aforesaid predetermined distance where relativelybright illumination is desired.

7. A road surface of such smoothness as to offer no materialinterference to the passage of a vehicle thereover and capable of beingrelatively brightly illuminated at substantial distances by a lightsource carried by the vehicle, said road surface comprising a pluralityof blocks, each having a reflecting surface departing from the verticalat an angle whose tangent is substantially the ratio of a predeterminedhei ht of a source of light positioned above the road surface at apredetermined substantial distance from and in front of such reflectingsurface to the horizontal distance between such light source and thereflecting surface, whereby in a substantially level section of roadwayto be illuminated as aforesaid at a distance of about three hundred feetfrom a vehicle on such roadway section and having lamps positioned atabout three feet above the roadway, such reflecting surfaces will bedisposed at an angle of approximately onehalf a degre from the vertical,said reflecting surfaces'being substantially normal to light beams fromsuch predetermined source and each of said blocks in the region of itsreflecting surface being higher from the horizontal than the remainingportions thereof.

8. A road surface of such smoothness as to offer no materialinterference to the passage of vehicles thereover and capable of beingrelatively brightly-illuminated at substantial distances by lightsources carried by the vehicles, said road surface comprising aplurality of reflecting surfaces each departing from the vertical at anangle whose tangent is substantially the ratio of a predetermined heightof a source of light positioned above the road surface at apredetermined stantial distance from and in front of such refleetingsurface, the top surface of said block meeting said reflecting surfaceat the top edge of substantial distance from and in front of such v v'being arranged in a plurality of groups of rows,

the rows of one group being disposed at an angle to the rows in anothergroup. i

9. A paving block having a sectional area of irregular form and havingan upstanding surface of good reflective quality disposed at such angleto the vertical as to be substantially normal to light beams from asource of light positioned above said block and at a predetermined,subthe latter and being disposed at an angle to the horizontal.

10. A road surface such as claimed in claim 1, in which said reflectingsurfaces are arranged in arcuately shaped rows extending transversely ofthe roadway and are each arcuately shaped so that each row of suchsurfaces present a substantially spherical segmental reflecting surfaceto the lightfrom the vehicle.

11. A highway for the normal travel of a vehicle at night, comprising aseries of upstanding surfaces of good reflective quality arranged to becontacted by lightoriginating on the vehicle,

said reflecting surfaces extending generally in a direction transverselyof said highway. and being inclined from the vertical at such angle asto be substantially normal to light beams emanating from the vehicle ata predetermined, substantial distance from and in front of suchsurfaces, said reflecting surfaces being spaced longitudinally in thedirection of the highway by surface portions each extending from the topedge of a preceding reflecting surface to below the next succeedingreflecting surface and having sufficient length to permit the light fromthe vehicle at such predetermined distance to contact sufllcient of saidreflecting surfaces in the aggregate to illuminate a portion of thehighway bearing said rejecting surfaces sufilciently to define suchportion relatively clearly.

12. A highway for the normal passage of a vehicle at night under theillumination of its own lights, comprising a plurality of reflectingsurfaces of good reflecting quality, said reflecting surfaces extendingtransversely of the highway and projecting upwardly in a generalvertical direction above the average height of the highway so as to beilluminated by the lighting means carried by the vehicle, saidreflecting surfaces having sufficient of the aggregate reflecting areathereof disposed at such angle to the vertical as to be substantiallynormal to light beams from the vehicle when the latter is positioned atabout 250 to 300 feet from and in front of such surfaces and beingspaced longitudinally along the highway by surface portions eachextending from the top edge of a'preceding reflecting surface to belowthe next succeeding reflecting surface and having suflicient length toenable the light from the vehicle at the stated distances to clearlydefine the portion of the highway having such surfaces under averagenight driving conditions.

EUGENE C. BINGHAM.

